1. Field of the Invention
The present invention relates to phase locked laser arrays, and more particularly concerns such an array having improved and simplified construction and improved control.
2. Description of Related Art
Multiple cavity waveguide lasers have a number of advantages in the desired goal of achieving small size, high power and light weight laser systems. Combining laser energy from multiple cavities not only may provide increased power for length of the laser, but enables delivery of a laser beam of greatly increased intensity. A multiple cavity clustered waveguide laser is described in a co-pending application of Alan R. Henderson for Clustered Waveguide Laser, Ser. No. 913,829, filed Sept. 30, 1986, and assigned to the assignee of the present application. The disclosure of this application of Henderson is incorporated herein by this reference, as though fully set forth.
Other waveguide lasers are disclosed in the following U.S. Patents: U.S. Pat. Nos. 4,577,323 to Newman et al, 4,103,255 to Schlossberg, 4,464,758 to Chenausky et al, 4,429,398 to Chenausky et al, 4,169,251 to Laakmann, and 4,129,836 to Papayoanou.
A type of multiple cavity waveguide laser which has sometimes been termed a "ridge waveguide laser" has been developed for phased locked arrays of coupled waveguide lasers. Such a ridge waveguide laser is described in detail in a Final Report dated July 30, 1985 entitled "Coupled High Power Waveguide Laser Research" prepared by L. A. Newman, A. J. Cantor, R. A. Hart, J. T. Kennedy and A. J. DeMaria and describing work performed under Air Force Contract F49620-84-C-0062. This is an unclassified Technical Report distributed by the Defense Logistics Agency of the Defense Technical Information Center. The waveguide laser array of the Newman et al Report employs far field interference of a number of phase locked waveguide lasers to provide a highly directional high power laser output. Such a system can deliver an intensity on target that is equal to the product of the single bore intensity and the square of the number of bores. Thus the resulting beam provides high power in a narrow beam footprint, or, effectively, greatly increased beam intensity. Phase locking of the energy oscillations in the several separate bores of the array of Newman et al is provided by optical coupling of laser energy through a gap at ends of very thin ceramic webs that are employed to divide the laser cavity into several separate but mutually coupled bores. The array of Newman et al is costly to manufacture because of the difficulty of grinding the ceramic body and the extreme fragility of the very thin dividing webs.
Where arrays of five or more adjacent bores are employed in the "ridge waveguide laser", thus resulting in a laser body of increased width, heat generated in the center of the body is dissipated more slowly than heat generated at outer portions of the body, and there is created a large transverse thermal gradient across the array. The thermal gradient produces different effective lengths of outer and inner bores of the array. Higher temperature produces lower gas density, lower gain and lower index of refraction. This causes the lasers of the respective bores of the array to operate at different frequencies, effectively de-locking the phased array, and thus preventing the desired phase locked operation of all the bores.
Accordingly, it is an object of the present invention to provide a phase locked laser array that avoids or minimizes above-mentioned problems.